Electric trucks include a wheel supported chassis, an electro-mechanical control unit, a silicon controlled rectifier, an hydraulic unit, an electric motor and a power pack. Mounted in or on a standard cowl, which is a portion of the chassis, are the silicon controlled rectifier, the operating pedals, brake cylinder, hydraulic units, and the electro-mechanical control units comprising circulating fan, hoist and directional contacts, potentiometer, fuses, terminals, cut out switches, and meter and indicators. Under normal operating conditions in a normal environment, the silicon controlled rectifier or SCR and the electro-mechanical units are exposed to the atmosphere as the SCR generates heat, which heat must be dissipated.
In the packing and/or freezing industry, the electric truck is operated under extremely cold conditions and in many cases there is a considerable amount of brine. Under the cold conditions, the electro-mechanical unit utilizes heaters to keep the equipment operable and dry. However, under brine condition, the SCR equipment and connections and the electro-mechanical unit and connections become corroded thus ultimately requiring the truck to be completely overhauled to prevent complete destruction to various components of the truck.
During overhaul or cleaning, the electric truck is out of service and either additional equipment must be made available or revised operating schedules must be utilized until the equipment is again operable.
It has also been found that a standard or conventional electric truck can contaminate the environment of a packing plant freezer and it therefore would be desirable to mount as much equipment as possible in controlled compartments wherein contamination can be held to a minimum or eliminated. Furthermore, the exterior of uncontrolled compartments cannot readily be worked by steam or hot water because of the effect of water on electrical equipment.
There are a number of hostile environments other than cold temperatures or brine; for example, carbon black dust and aluminum dust or fumes. These dusts are conductive and contaminative, and as such, create short circuits in the silicon collector rectifier, in electronic gear, and in the electro-mechanical gear. An investigation of the art fails to disclose any attempt to alleviate the problems set out above.